Helical pipe making method

ABSTRACT

Apparatus for and method of helically forming pipe from an elongated strip of metal. The elongated strip is curled between the rolls of a three-roll strip curling apparatus into a curved path, with the rolls exerting lateral forces on the strip during curling for guiding the strip so that such curved path is in the form of a helical convolution in which the trailing edge of a preceding portion of the strip converges into contact with the leading edge of a following portion thereof.

United States Patent Davis [451 Mar. 21, 1972 54 HELICAL PIPE MAKINGMETHOD 3,093,103 6/1963 Berkeley ..29/4773 3,146,331 8/1964 Schubert..228/17 X [72] Invent Paul Alameda 3,269,005 8/1966 Smith et a1..29/477.3 [73] Assignee: Pacific Roller Die Co., lnc., Hayward,3,314,141 4/1967 Bacroix ..29/477.3

Calif.

. Primary Examiner-John F. Campbell 4 969 [22] Filed Feb 1 AssistantExaminerRichard Bernard Lazarus [21] Appl- N -I 796,437 Att0rneyBoyken,Mohler, Foster and Schwab 52 us. Cl ..29/4777, 29 477, 29/4773. [571ABSTRACT 228/17 Apparatus for and method of helically forming pipe froman [51 Int. Cl ..B23k 31/02 elongated Strip of metaL The elongated Stripis curled between [58] Fleld of Search ..29/477, 477.3, 477.7; 228/17,the rolls of a u Strip curling apparatus into a curved 228/44 49 path,with the rolls exerting lateral forces on the strip during curling forguiding the strip so that such curved path is in the [56] Referencescued form of a helical convolution in which the trailing edge of aUNITED STATES PATENTS preceding portion of the strip converges intocontact with the leading edge of a following portion thereof. 1,884,65810/1932 Gladkov et al.... ..228/17 2,752,873 7/1956 Freeze "29/4773 3Claims, 9 Drawing Figures PAIENTEnmm I972 3.650.015

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HELICAL PIPE MAKING METHOD BACKGROUND OF THE INVENTION This inventionrelates to apparatus for and a method of making pipe and, moreparticularly, to helically forming metal pipe from an elongated strip ofmetal.

Pipe formed as herein described may be of the smooth wall type, such asemployed in conveying solid materials or petroleum products; or it maybe corrugated pipe, of the type used for underground drains, culverts,and the like. Pipe diameters may range from 6 inches to in excess of 96inches. Bending or curling of the strip material from which such pipe isformed normally requires the application of very large bending forces.The metal material thickness in smooth wall pipe may exceed one-eighthinch, and corrugated material, while normally is not as thick as thatused in the smooth wall pipe, offers great resistance to bending. Whenbending the strip by application of great bending forces, the problem ofadequate control of the strip for proper engagement and joinder of thestrip edges is of critical importance.

Known methods and forms of machines employed in fabricating pipe bycurling an elongated strip of metal into helical convoultions andjoining adjacent edges of the strip at a welded seam, lock seam, or thelike, have involved forcing the strip around a stationary mandrel.Inherent in such prior machines and methods are objectionably greatfriction and uneven stressing of the strip, with less than effectivecontrol of the strip. In other machines and methods heretofore used orproposed, the strip is forced against unrestrained or freerolling casterrollers or ball type forming elements which cannot accomplish anycontrol of the strip.

Further, so far as is known to applicant, prior machines for forminghelical pipe have been restricted to formation of a single size, orrequire extensive adjustment or modification each time pipe diameter ischanged, which interrupts pipe production.

SUMMARY OF THE INVENTION In the helical pipe making apparatus and methodof this invention means are provided for advancing an elongated strip ofmetal in a generally planar path along its longitudinal axis for feedingto a forming device at which the strip is curled between three sets ofrollers into helical convolutions. The sets of rollers extend in rows atan angle relative to the longitudinal axis of the incoming strip,suchangle being so related to the radius of the convolutions and the widthof the strip that the trailing edge of a preceding portion of the stripconverges into contact with the leading edge of the following portion ofthe strip. The peripheries of the rollers of the three sets exertlaterally directed forces against the strip surfaces for guiding thestrip, and the positioning of the peripheries of the rollers of at leastone set is precisely adjustable for so guiding the strip such that thedesired contact between said trailing and leading edges is effected andmaintained.

It is, therefore, a principal object of this invention to provide anovel and improved apparatus for and method of curling an elongatedstrip of flat metal into helical pipe, in which a desired relationshipbetween the trailing edge of the preceding portion of the strip and aleading edge of the following portion of the strip is precisely effectedand maintained.

Another object of the invention is provision of an apparatus for andmethod of curling an elongated strip of metal into helical pipe,effecting a high degree of control over the strip where the thickness orcharacter of such strip requires the application of extremely largebending forces.

A further object of the invention is the provision of a helical pipeforming apparatus and method yielding greater strip control thanheretofore with a minimum of friction between the apparatus and materialof the pipe.

An additional object of the invention is the provision of an apparatusand method of the above character which is readily adaptable toformation of pipe of different diameters.

Other objects and advantages of the invention will become apparent fromthe following description of a preferred embodiment of the invention.

bodying a preferred form of this invention;

FIG.- 2 is a top plan view of the pipe curling or forming portion of theapparatus of FIG. 1, on a scale enlarged relative thereto;

FIG. 3 is a vertical sectional view of the pipe curling portion of FIG.2 as seen from line 33 of FIG. 2 on a scale enlarged relative thereto;

FIG. 4 is a fragmentary top plan view of sets of curling rollers andassociated structure, as seen from line 4-4 of FIG. 3;

FIG. 5 is a simplified top plan view illustrating the sets of curlingrollers and the manner in which they guide the strip for effecting andmaintaining desired contact between opposite edges of the strip.

FIG. 6 is a vertical sectional view taken along line 6-6 of FIG. 5,showing rollers of the set which first contacts the strip and the mannerof contact between the rollers and the strip;

FIG. 7 is a vertical sectional view taken along line 77 of FIG. 5,showing rollers of the second set to contact the strip and the manner ofcontact between roller and strip;

FIG. 8 is vertical sectional view taken along line 88 of FIG. 5, showingrollers of the third set to contact the strip;

FIG. 9 is a vertical sectional view taken along line 9-9 of FIG. 8,showing the rollers of FIG. 8 and the manner in which they contact thestrip.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the helicalpipe making apparatus of this invention comprises an elongated carriage2 supported on ground wheels 11, and stationary frame 12 adjacent an endof carriage 2 and supporting a strip curling or forming device 7. On theend of carriage 2, remote from curling device 7, is a coil handlingmeans 4 for a strip 3 of metal material in coiled form. Adjacent coilhandling means 4, there is preferably provided a strip separating orpeeling means 6, and at successive stations along carriage 2 are aplurality of strip drive rolls 10. On frame 12, which supports stripcurling device 7, there is also a welding station 8 at which theopposite edges of strip 3 are joined for completion of the pipe 20 (FIG.1). The completed pipe discharges at a pipe discharge station 9.

Coil handling means 4 may be any suitable means for supporting thecoiled strip 3 for rotation about an axis to enable uncoiling, andpreferably includes provision for rotating the coil for initiating suchuncoiling and advancement of strip 3 in a path along its longitudinalaxis. Straightening of strip 3 from the coiled to a generally planarform is facilitated by peeling means 6 having a series of blades 29supported for interposition between the coiled portion of the strip andadjacent longitudinally advancing portion.

Strip drive rolls 10 are arranged in a plurality of stands or pairs,each having an upper roll and lower roll, and the stands of rolls 10 aregenerally horizontally aligned so that strip 3 will pass between theupper and lower rolls thereof. The shafts 14 of each stand are supportedin bearings 15 at one end. The other end of shafts 14 extend through abearing 16 to connection with gear box 17, each of such gear boxinterconnecting the upper and lower rolls 10 of each stand for drivingtogether, and all gear boxes 17 being connected by coupling shafts 18and to drive motor 19 as by pulley drive 22, so that all rolls 10 aredriven together at the same speed. The upper rolls 10 of each stand arevertically adjustable by any suitable means for effecting proper spacingbetween the upper and lower rolls corresponding to the thickness of thestrip 3 passed therebetween for being driven by the rolls toward thecurling device 7. Located beyond the leading stand of drive rolls 1'0and projecting from the end of carriage 2 and to frame 12, are a pair ofelongated edge guides 27 (FIGS. 1, 2 and 3) extending in the directionof advance of strip 3 for guiding the strip therebetween, and includingan upper flange portion 30 (FIG. 3) and lower flange portion 31 betweenwhich the edge portion of strip 3 is confined for preventing the stripfrom being curved substantially from the generally planar form.

The curling device 7 supported on frame 12 (FIGS. 2 and 3) comprises anassembly of three parallel forming rolls including, in the order inwhich they contact the advancing strip, a lead roll 32, a mandrel roll33, so denominated because it is disposed internally of the path of thecurled strip 3, and a buttress roll 34. Rolls 32 and 33 are mounted sothat opposite surfaces of incoming strip 3 are engaged thereby, andbuttress roll 34 is supported on the opposite side of mandrel roll 33from lead roll 32, remote from carriage 2, and is offset upwardly (FIG.3) from the feed path represented by the plane of strip 3 and is adaptedto engage the same surface of strip 3 as roll 32. Rolls 32, 33 and 34function to curl strip 3 into an arc with mandrel roll 33 serving as afulcrum as strip 3 is driven therethrough by drive rolls 10.

Although in the preferred form, rolls 32, 33 and 34 are constructed of aplurality of individual rollers, each said roll may be consideredgenerally as a unitary roll having an axis parallel to a pipe axis 35(FIGS. 1, 3) about which strip 3 is curled, said axis 35 extending at anoblique angle relative to the longitudinal axis of incoming strip 3.Supporting the rolls 32, 33 and 34 with their axes at an oblique angleto the feed path of strip 3 causes said strip to be curled by said rollsinto helical convolutions, the pitch angle of which is the same as saidoblique angle less 90. In order to support said rolls at selecteddifferent oblique angles relative to the feed path of strip 3, and arm36 (FIGS. 1, 3) rigid with carriage 2, extends outwardly from the outputend thereof, and has its outer end swingably mounted about a generallyvertical pivot pin 37 (F IG. 3) fixed with respect to the frame 12 ofcurling device 7. Carriage 2 is therefore supported on ground wheels 1 lfor swinging relative to frame 12 about pivot pin 37 which is locatedwith its axis generally intersecting the pipe axis 35 and extending froma point substantially directly below the leading longitudinal side edge39 (FIGS. 1, 2) ofstrip 3.

The oblique angle between the feed path of strip 3 on carriage 2 androlls 32, 33 and 34 may be adjusted in relation to the width of strip 3so that the trailing edge 38 (FIGS. 1, 2) of the preceding portion ofstrip 3, when curled through a convolution of 360 (FIG. 2), engages theleading edge 39 (FIGS. 1, 2) of a following portion of said strip. Inthis manner, strip 3 is curled into closed, continuous, helicalconvolutions the adjacent edges of which may be joined to complete acontinuous pipe discharged from curling device 7 along pipe axis 35.

Because of imperfections of the strip 3, in uneven thickness, width, orhardness in different portions, or camber (i.e., the edges are notstraight and parallel), or other differences between the actual and thetheoretical, the strip may not always follow the path calculated fromthe width, diameter, and helix angle factors. For this reason, sometrial and error in effecting fine adjustments to bring the adjacentedges of the convolutions into engagement is often required. Inaddition, when the seam is joined by welding, more or less pressure maybe desirably exerted axially of the edges depending on the type ofwelding system employed.

It has been found that such adjustment readily can be effected byslightly changing the angle of the rollers of the forming rolls, mostparticularly rollers 95 of mandrel roll 33 and secondarily rollers 67 ofbuttress roll 34. Since movement of the edges of strip 3 toward and awayfrom each other has been effected by such adjustment, it is believedthat the strip 3 tends to follow a line in a plane perpendicular to theaxis of rotation of the roller over which the strip is being curled. Itis understood that the forming rolls must extend at an oblique angle tothe longitudinal axis of the strip in order to form it into helicalconvolutions. If any f the rolls, particularly mandrel roll 33 were asolid, elongated cylinder, strip 3 would tend to follow a pathperpendicular to the roll axis and the pipe axis rather than along theproper helix angle.

The effect of comprising the forming rolls of individual rollers, eachmounted with its axis of rotation substantially perpendicular to thelongitudinal axis of the strip is to orient the surface of the rollerwhich engages the strip so that it moves in the same direction as a truehelix for the strip width, pipe diameter and angle involved. It willalso be noted that the axes of rotation of the rollers are absolutelyperpendicular to the strip axis in the theoretical condition that thestrip is in planar condition where it engages the rollers. Since thestrip is substantially curved at engagement with buttress roll 34, theaxes of rotation of rollers 67 are offset from the perpendicular to theextent necessary to meet the above-described condition of movement ofthe roller surface and strip at point of contact. By means to bedescribed, the fine adjustment of the positions the rollers of rolls 32,33, 34 may be accomplished whereby the strip is guided during curlingwith a high degree of precision for effecting and maintaining desiredengagement between opposite edges 38, 39.

Rolls 32 and 34 are supported on the base 42 of frame 12 (FIGS. 2, 3,4). Roll 32 comprises a plurality of disc-shaped rollers 43 (FIGS. 3,4), each having a periphery 124 preferably of slightly rounded contour.The individual roller 43 is mounted for rotation in a generally verticalplane about a pin 45 and within an upstanding yoke 44 fixed on an end ofan elongated mounting plate 46. Mounting plate 46 rests on an elongatedmounting block 48 fixed on base 42 and extending in the directionparallel to the desired direction of extent of pipe axis 35, and a pin55 (FIG. 3), integral with mounting plate 46 and having an axisintersecting the axis of pin 45 at its midpoint, projects downwardlyinto a bore 53 in the upper portion of mounting block 48 for pivoting ofmounting plate 46 thereabout on the mounting block 48. Mounting plates46 each include a tail portion 47 (FIGS. 3, 4) and are interconnectedfor pivoting together by a rod 56 extending longitudinally of mountingblock 48 pivotally connected to the outer end of the tail portion 47 ofeach mounting plate 46. The end 59 of mounting plate 46 oppositetherefrom is rounded and abuts against an elongated gib 57 (FIG. 3)fixed to and extending longitudinally of mounting block 48, andincluding a portion 58 which overlies end 59 of mounting plate 46. Gib57 with portion 58 provides a way within which end 59 of mounting plate46 slides during pivoting thereof.

The disc shaped rollers 67 (FIGS. 3, 4) of buttress roll 34 are mountedin similar but reversed fashion relative to the path of the incomingstrip 3, and each has a rounded periphery 125 that is angled relative tothe roller axis as hereinafter more fully described. There are providedyokes (FIG. 3) 63, mounting plates 62, mounting block 60, pivot pins 61,connecting rod 64 and gib 65, all corresponding to similar partsassociated with lead roll 32. Mounting block 59 is of greater thicknessthan mounting block 48 for elevating the rollers 67 of roll 34 relativeto rollers 43. Further, mounting block 59 is slidable on base 42 indirections toward and away from roll 32 between a pair of ways 68 (FIGS.2, 3) in engagement with and overlying the opposite ends 71 thereof(FIG. 2). Ways 68 extend in a direction normal to the direction ofextent of mounting block 60 so that it is maintained parallel tomounting block 48. Means for effecting sliding of mounting block 60includes a spaced parallel pair of threaded rods 70, 73 (FIGS. 2) fixedto mounting block 59 at the side 74thereof remote from carriage 2,through connecting collars 75. Rods 70, 73, respectively, are freelyreceived through bearing blocks 80, 83 fixed on the edge 76 of base 42remote from carriage 2. Rod 70 is also received through a sprocket wheel77 connected to the outer side of bearing block 80 and for rotationrelative to said block 80 and having an internally threaded hub 81 whichcarries a handle 82. Threaded rod 73 is received through an internallythreaded sprocket wheel 79 connected to the outer side of bearing block83 for rotation relative thereto. A continuous chain 78 is engagedaround sprocket wheels 77, 79 for rotation together of the sprocketwheels upon turning of handle 82, whereby rods 70, 73 are screwedthrough sprocket wheels 77, 79 for drawing or pushing mounting block 60,depending on the direction of rotation of handle 82.

At the end of frame 12, remote from pipe discharge station 9, is a frameend portion 84 (FIGS. 2, 3) providing an upper generally horizontalsurface 85 elevated with respect to the upper surface of base 42, and onwhich is supported an arm structure generally designated 86 (FIGS. 2,3). Arm structure 86 extends from frame portion 84 in the direction ofpipe axis 35 above and across the path of incoming strip 3, andcomprises a lower bolting block 87 for bolting to frame end portion 84on surface 85, and structural members including lower arm member 88 andside members 90 having upper surfaces 89 inclined downwardly from apoint slightly inwardly of bolting block 87 toward the free end of armmember 88. The combination of bolting block 87 and structural members88, 90 provides an overhanging arm structure 86 of great rigidity andstrength. At the underside of arm member 88 is the mandrel roll 33comprising a plurality of roller mounting plates 93 (only one of whichis shown in FIG. 3), each being connected to arm member 88 by a pivotpin 97 for pivoting about a generally vertical axis. Depending frommounting plate 93 are the legs of a yoke 94 which receives disc shapedroller 95 with rounded periphery 126, for rotation in a generallyvertical plane about a pin 96 directly below pivot pin 97. The pluralityof mounting plates 93 with the rollers 95 extends parallel to rolls 32,34, i.e., parallel to pipe axis 35. Mounting plates 93 slide at one end98 within a way 99 extending parallel to pipe axis 35, and the oppositeends 100 of the mounting plates 93 are pivotally interconnected by a rod102. Thus, roller 33 is constructed in similar fashion to rolls 32, 34,but with rollers 95 lowermost. A single size and form of arm structure86 may be employed in forming most diameters of pipe. However, informing pipe in the smallest diameters, e.g., 12 inches and smaller, anarm structure of a size most desirably used in forming larger diameterpipe with roll 33 may be too large to be accommodated within the curledstrip, and a smaller arm structure will be utilized. Bolting block 87facilitates removal of arm structure 86 for interchanging with thesmaller arm structure.

In each of the rolls 32, 33 and 34 the associated rollers are parallel,i.e., the peripheries of the rollers of a particular roll lie inparallel planes, and parallel relationship is maintained during pivotingby the associated one of connecting rods 56, 64 or 102. Precisepositioning of rollers 43 of lead roll 32 is effected through use ofroller adjusting means 105 (FIGS. 2, 3, 4). Similar adjusting means 106(FIG. 3) and 107 (FIGS. 2, 3, 4) are associated with mandrel roll 33 andbuttress roll 34, respectively. Roller adjusting means 105 includes ahorizontally disposed bracket 108 (FIG. 4) fixed to frame 12 at a pointgenerally in line with connecting rod 56, and secured on bracket 108 forpivoting about a vertical axis is an internally threaded sleeve 109. Anarm 112 formed integrally with the mounting plate 46 that is nearestframe portion 84, projects from the end of the tail portion 47 thereof,and pivotally carries an internally threaded sleeve 113, with thethreads of sleeve 113 in alignment with and oppositely directed fromthose of sleeve 109. Sleeves 109, 113 respectively receive theoppositely threaded end portions 114, 115 of an adjusting rod 116 havinga central nut portion 117 for gripping by a wrench or the like. Turningof adjusting rod 116 in one direction causes connecting rod 56 to bedrawn toward the bracket 108 and mounting plates 46 with rollers 43 tobe pivoted in the corresponding direction about pins 53. Oppositeturning of adjusting rod 116 causes connecting rod 56 to be displacedfrom bracket 108 with resulting corresponding opposite pivoting ofrollers 43. Roller adjusting means 106 of mandrel roll 33 similarlyincludes an adjusting rod 118 for causing pivoting of rollers 95 throughan arm 119 integral with the roller mounting plate 93 nearest frameportion 84, and roller adjusting means 107 of buttress roll 34 has acorresponding adjusting rod 122 operatively connected to roller 67through an arm 123.

In the preferred construction of the curling device 7, rollers 43 oflead roll 32 are positioned with the uppermost portion of the rollerperiphery 124 (FIG. 3) projecting into the planar feed path of strip 3,said strip being slightly curved out of and above such path at contactwith rollers 43. The lowermost portion of the periphery 126 of rollers95 in mandrel roll 33 engages strip 3 directly below pipe axis 35, androllers 95 are vertically positioned such that they cause strip 3 to becurved from such position above the planar feed path downwardly to thelevel of the path. Strip 3 is thus slightly curved toward periphery 126of roller 95, immediately ahead of as well as beyond the roller as thestrip is curled therearound. The upper portion of the periphery 125 ofroller 67 in the upwardly offset buttress roll 34 engages strip 3 forcurling it into an arc, the diameter of which is determined by thehorizontal spacing between roll 34 and mandrel roll 33, which spacing isreadily adjustable by rotation of handle 82.

Surface contact between the peripheries of the sets of rollers 43, 67and 95 and strip 3 yields a high degree of control over the lateralpositioning of the strip during curling as a result of the applicationof substantial lateral forces on the strip. By adjustment of thepositions of the rollers through adjusting means 105, 106 and 107, thestrip can be effectively maintained in a desired lateral position ordisplaced laterally from an incorrect to a desired position, for properconvergence of opposite strip edges 38, 39.

Given a particular width of strip 3 and the diameter of pipe to beformed therefrom about a pipe axis 35 (FIG. 5), a particularpredetermined angle must be maintained between the longitudinal axis ofstrip 3 as it arrives at lead roll 32 and the pipe axis 35 to yield pipein which the trailing edge 38 of a preceding portion of strip 3 willconverge into engagement with the leading edge 39 of a followingportion. Specifically, the oblique angle between the longitudinal axisof strip 3 and pipe axis 35 is to be equal to the pitch angle ofconvolutions forming the pipe plus As seen in FIG. 2, an indicator rod127 adjustably mounted on arm structure 86 and having a pointer 128 maybe employed immediately ahead of lead roll 32 for locating the correctposition of the incoming strip and providing indication of lateralshifting of the strip from the correct position by reference to stripedge 39.

In FIG. 5, pointer 128 is schematically illustrated at edge 39 of strip3 that is correctly positioned as it arrives at lead roll 32, asdescribed, so that opposite edges 38, 39 converge into engagement as atthe seam line 131 (FIG. 5) as the strip is curled by rolls 32, 33 and34, into helical convolutions. For maintenance of such positioning ofstrip 3, rollers 43, 67 and are positioned for movement of theirperipheries 124, and 126, respectively, in the direction of movement ofthe correctly positioned strip, at contact with the rollers, i.e., eachroller 43 (FIGS. 5, 6) 67 (FIGS. 5, 9) and 95 (FIGS. 5, 7) is disposedin a vertical plane that extends in the direction in which the correctlypositioned strip is moving at contact with that roller. With specificreference to roll 33 (FIGS. 5, 7) where a roller contacts strip 3 at thestrip edge, e.g., roller 95a, it is positioned so that the direction ofmovement of its periphery 1260 is in a vertical plane that includes thetangent to the correctly positioned strip edge (38 or 39) at the pointalong the edge at which the roller contacts the strip. The remainingrollers 95 are parallel to roller 95a, so that at contact with strip 3the peripheries 126 of all rollers 95 move in directions parallel to thedirection of movement of roller periphery 126a. As seen in FIG. 5, thedirection of movement of strip 3 changes as it undergoes difi'erentstages of curling at rolls 32, 33, 34, respectively. Correspondingly,the roller peripheries of a particular one of rolls 32, 33, 34 move indif- 'ferent directions than the roller peripheries of the other tworolls, i.e., the vertical planes of the rollers of a roll are angularlydisposed relative to the planes of the rollers of the other two rolls.

Curling of strip 3 occurs about a horizontal pipe axis 35 that extendsat an oblique angle with respect to the longitudinal axis of the strip.The individual rollers 43, 67, 95 have axes of rotation 50, 51, 52,respectively (FIG. which extend at an angle with respect to pipe axis35, such axes being horizontal and normal to the direction of movementof the strip at contact with such roller. Consequently, with respect tothe direction of extent of axes 50, 51, 52 strip 3 is laterally inclined(FIGS. 6, 7, 9). In FIG. 7 it is seen that at contact with periphery 126of a mandrel roller 95 strip 3 is inclined upwardly from edge 39.Periphery 126 has a slightly rounded contour for approximating thecontour of the portion of the strip which it contacts to prevent thestrip from riding on a corner of the roller. Further, the area ofcontact between strip 3 and the periphery of roller 95 is maximized,which is of considerable importance, since increased contact contributesto increased control of the strip.

Strip 3, at contact with periphery 124 of a lead roller 43 (FIG. 6) isinclined downwardly from edge 39, to a slight degree, because of theslight curl imparted to the strip as it is curved around roll 32, andperiphery 124 has a rounded contour, whereby the strip surface isprevented from engaging the corner of the rollers and contact betweenstrip and roller max imized. At contact with the external buttressrollers 67, (FIGS. 5, 8, 9) strip 3 is curled upwardly away from saidrollers into substantially its final curvature, and in the direction ofextent of the roller axis of rotation 51, is inclined upwardly from edge39 (FIG. 9) to a greater degree than at contact with mandrel rollers 95.Periphery 125 of roller 67 has a surface contour that is rounded andangled with respect to axis 51. Such surface contour enables the rollerto provide a generally flat contact surface though the angle ofinclination of the contacting portion of strip 3, with respect to axis51, may differ within a wide range depending on the diameter of pipe tothe formed, width of strip 3 and other geometric factors.

When the rollers of any or all of rolls 32, 33, 34 are oriented so thattheir peripheries do not move in the direction in which the properlypositioned strip is moving at contact with suchrollers, lateral forcesbetween the rollers e.g., 43', 95' and 67 of FIG. 5, and properlypositioned strip create increased friction and stressing. Such forcestend to cause a lateral shifting of the strip, as indicated by edges 38,39' (FIG. 5), yielding improperly formed convolutions such as withdisplaced edges 38', 39. Incorrect positioning of rollers at an angleoffset to the other side of correct may cause overlapping or deformationof edges 38, 39. The area of contact between strip 3 and a roller 95 isgreater than that between the strip and rollers 43, 67, and greaterforces are exerted on the strip by roller 95 then by other rollers.Therefore, adjustment of rollers 95 through positioning means 106 willbe most efiective in maintaining proper positioning of strip 3.

In operation, carriage 2 and frame 12 are initially relativelypositioned at an oblique angle determined by the width of strip 3 anddesired diameter of completed pipe 20, roll 34 is positioned along ways68 through handle 82, and the sets of rollers 43, 67 and 95 arepositioned through adjusting means 105, 107 and 106, respectively. Thestands of drive rolls (FIG. 1) on carriage 2 advance strip 3 in thedirection of its longitudinal axis along a planar feed path. In the caseof a new coil of strip material, coil handling means 4 advances strip 3until the leading edge thereof engages the first stand of drive rolls10. At the leading or output end of carriage 2, immediately ahead oflead roll 32 of forming device 7, strip 3 is passed between edge guides27 (FIGS. 1, 2), including upper and lower horizontally extending flangeportions 30, 31, respectively, (F IG. 2), which vertically confine strip3 for preventing objectionable buckling which might otherwise occur whenthe advancing strip encounters curling rolls 32, 33 and 34. Edge guides27 permit strip 3 to be slightly upwardly curved from the planar path bylead roll 32, so that the strip upper surface is slightly above thebottom surface of the rollers of mandrel roll 33 until the strip iscurved downwardly thereby, by which arrangement, the area of contactbetween strip 3 and each roller 95 is increased.

As strip 3 passes and is bent against mandrel roll 33 by lead roll 32and buttress roll 34, it is curled about pipe axis 35 into helicalconvolutions, and it can be determined if the incoming strip 3 iscorrectly positioned by noting whether adjacent strip edges 38, 39 ofconvolutions converge into proper engagement at a point lyingsubstantially within the plane of the strip feed path, directly belowpipe axis 35. When the strip is incorrectly positioned, rollers of roll33 may be adjusted through adjusting means 106 to laterally shift thestrip, rollers 43, 67 may be correctly positioned with their peripheriesmoving in the direction of movement of the strip at contact, and pointer128 may then be located at the correctly positioned edge 39. Duringcurling, a high degree of control is maintained over the strip 3 byrollers 43, 67 and 95, such that lateral shifting is held to a minimum.Should such shifting occur, however, the strip readily can berepositioned by adjusting the positions of rollers 95 through adjustingmeans 106.

Finally, the adjacent edges 38, 39 of the curled strip are welded byconventional means (not shown) at welding station 8 to complete pipe 20which is discharged for further handling at discharge station 9.

From the foregoing, it can be appreciated that this invention provides amethod of forming pipe from an elongated strip which is advanced in aplanar path along its longitudinal axis. The advancing strip iscontacted at one surface by contact surfaces disposed in a first rowextending out an oblique angle to the longitudinal axis of the strip.The strip is next passed between a second parallel row of contactsurfaces contacting the other surface of the strip, and a third parallelrow of contact surfaces, contacting the one surface of the strip in aplane different from the plane of the advancing strip, for curling itinto helical convolutions of a given radius about a pipe axis extendingat the same oblique angle relative to the longitudinal axis of thestrip. The oblique angle is related to the radius of the convolutionsand the width of the strip such that adjacent edges of the strip ascurled into such convolutions converge into engagement. The contactsurfaces of at least the second row move in the direction in which thestrip moves at contact therewith when the strip is positioned forcurling into helical convolutions with engaged adjacent strip edges. Themethod yields a high degree of control over the strip with a minimum ofobjectionable friction between strip and contact surface.

It is to be understood that the claims appended hereto are intended tocover all changes and modifications of the example herein chosen forpurposes of disclosure which do not depart from the spirit and scope ofthe invention. For example, the stands of rolls on carriage 2 mayinclude strip corrugating rolls for production of corrugated pipe, andin place of a welded seam, the strip edges may be bent and interengagedto form a lock seam. Further, instead of manually operated adjustingmeans 105, 106 and 107, means for adjusting the positions of curlingrollers may be automatically actuated responsive to sensing means whichsense a shift in position of strip 3.

I claim:

1. A method of helically forming pipe from an elongated strip of metalhaving parallel side edges, comprising:

a. advancing said strip in a substantially planar feed path along thelongitudinal axis of said strip;

b. rollingly engaging one surface of said strip with a plurality ofrolling contact surfaces disposed for intercepting said feed path alonga first row extending at an oblique angle relative to said longitudinalaxis;

c. rollingly engaging the other surface of said strip with a pluralityof rolling contact surfaces disposed for intercepting said feed pathalong a second row extending at said oblique angle relative to saidlongitudinal axis; rollingly engaging said one surface of said stripwith a plurality of rolling contact surfaces disposed for interceptingsaid feed path along a third row extending at said oblique angle atpoints offset to one side of said feed path for curling said striptoward said contact surfaces extending along said second row, into acurved path of a radius about a pipe axis extending at said obliqueangle;

e. controlling movement of said strip along the rotational axes of saidrolling contact surfaces of said first, second and third rows byproviding frictional forces between said strip and said rolling contactsurfaces of at least said second row and constraining said surfaces ofat least said second row to rolling movement in the same direction as atrue helix line for said angle, for the width of said strip and for theradius of said path at the points of engagement of said surfaces andsaid strip; whereby the trailing edge of a preceding portion of saidstrip converges into engaging relation with the leading edge of afollowing portion of said strip to form a seam along said edges.

1. A method of helically forming pipe from an elongated strip of metal having parallel side edges, comprising: a. advancing said strip in a substantially planar feed path along the longitudinal axis of said strip; b. rollingly engaging one surface of said strip with a plurality of rolling contact surfaces disposed for intercepting said feed path along a first row extending at an oblique angle relative to said longitudinal axis; c. rollingly engaging the other surface of said strip with a plurality of rolling contact surfaces disposed for intercepting said feed path along a second row extending at said oblique angle relative to said longitudinal axis; d. rollingly engaging said one surface of said strip with a plurality of rolling contact surfaces disposed for intercepting said feed path along a third row extending at said oblique angle at points offset to one side of said feed path for curling said strip toward said contact surfaces extending along said second row, into a curved path of a radius about a pipe axis extending at said oblique angle; e. controlling movement of said strip along the rotational axes of said rolling contact surfaces of said first, second and third rows by providing frictional forces between said strip and said rolling contact surfaces of at least said second row and constraining said surfaces of at least said second row to rolling movement in the same direction as a true helix line for said angle, for the width of said strip and for the radius of said path at the points of engagement of said surfaces and said strip; wHereby the trailing edge of a preceding portion of said strip converges into engaging relation with the leading edge of a following portion of said strip to form a seam along said edges.
 2. The method of claim 1, including: f. joining said side edges of said strip so curled into said curved path for forming a pipe seam.
 3. The method of claim 1, wherein: f. said rolling contact surfaces of said first, second and third rows are positionable to move only in the direction in which said strip moves at contact therewith, when said strip is positioned for curling into said curved path. 